A press of the above-described general type is disclosed in German Patent Specification No. 2724060. Presses of this type have since been further developed in order to achieve a higher output. For this purpose, it has proved necessary to extend the pressing section, while the time taken for the binding agents to harden or set has remained constant. In the case of rotary presses, that is to say, presses having a rotating drum, wherein the pressing occurs between the outer casing of the drum and an endless steel belt, which belt passes part-way around the periphery of the drum and is subjected to tensile stress, an extension of the pressing section necessitates an increase in the diameter of the drum employed. The most modern presses of this type have drums with a diameter of 5 m, a roller surface length of about 3 m and a drum weight of about 110 tons.
Such large presses suffer from certain disadvantages because, due to the necessity of providing mounting and manufacturing tolerances which permit the press to start-up and to operate when empty. By providing these tolerances, damage is sustained by the endless steel belt, by the outer drum casing and by the guide rollers, which rollers simultaneously apply a pressure. This is because these machine parts are in contact with one another, metal-to(--)metal, if no material is being pressed therebetween.
On the other hand, the output achieved by enlarging the drum diameter from, for example, 3 meters to 5 meters is substantially improved. Thus, it is possible to process continuously a web having a thickness of 3 mm, thereby producing an output of up to approximately 40 m/min. This represents, on average, an output increase in excess of 200%.